1. Field of the Invention
The present invention relates to RF tags, and apparatuses and systems using the same, and more particularly to a RF tag attitude detection system for detecting the attitude of an article with a RF tag, and a RF tag and RF tag attitude detection apparatus used in the system.
2. Related Art
Heretofore, there has been proposed a method of retrieving the position of an article by mounting an RF tag (Radio Frequency tag) on the article during the course of distribution to use an RF tag retrieval apparatus equipped with a directional antenna (refer to Japanese Patent Application Laid-open No. 2002-271229). Also, there has been hitherto proposed a method of identifying the position of an article based on a phase difference of response signals from an RF tag (refer to Japanese Patent Application Laid-open No. 2003-101550).